Dutch Black-tailed Godwit numbers down by nearly 75%

Colour-rings and radio-tracking are helping to chart the ongoing decline of the Dutch Black-tailed Godwit population.

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A Portuguese rice field, full of limosa Black-tailed Godwits; most are Dutch breeders

The Black-tailed Godwit is the national bird of the Netherlands, the country in which the vast majority of the West European limosa race breed. These Dutch birds are an important part of the country’s cultural heritage and are of major international significance. Large amounts of money have gone into supporting the species, and the meadows that they share with others such as Redshank and Snipe, but efforts so far have failed to reverse a Black-tailed Godwit decline that has been going on since at least the 1970s. This negative situation is in stark contrast to the increases seen in the islandica subspecies that breeds in Iceland and winters in countries between Scotland and Spain. (There’s a comparison of the two subspecies in this WaderTales blog)

Counting Black-tailed Godwits

vero-pretty-flockIt is often easier to measure changes in numbers of waders on the wintering grounds, when birds are in flocks, than when pairs are thinly spread across their breeding ranges. For Dutch Black-tailed Godwits, most of which spend the winter in African countries, south and west of the Sahara, however, the best opportunity to monitor population trends occurs in Spain and Portugal in February, when the birds are on their way back to breed.

Each year a small group of ornithologists visit key sites in Extremadura, the Doñana Wetlands and the rice fields of the Tagus Estuary, to count flocks of birds and to look for colour-ringed birds. They’re able to use these counts and sightings of colour-ringed birds to assess what has happened to numbers in the previous twelve months.

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grutto met ringen (ringed Black-tailed Godwit)

In three of the years since 2007 they’ve witnessed increases but in most years the numbers have gone down. As February 2017 approaches, what will this year’s score be? How many of last year’s birds will have died and how many chicks hatched in 2015 and 2016 will be making the migratory journey north for the first time?

When assessing how many breeding godwits there are in the Netherlands the researchers collect and use the following information:

  • Counts of birds seen in flocks in Spain and Portugal.
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    It’s not always easy to see the colour-rings in rice fields

    Counts of colour-ringed birds. There’s a great one-line comment in the newly-published paper that forms the basis of this blog: ‘In total, we checked 420,206 godwits for colour-rings at Spanish and Portuguese staging sites’. That’s a lot of legs – and a huge effort.

  • An assessment of the proportion of islandica Black-tailed godwits in the flocks, so that they can be removed from the estimation process. This proportion had been established previously but were also monitored using sightings of colour-ringed birds of the islandica and limosa subspecies, and by taking account of the proportion of each population that wears rings.
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    Rosemarie Kentie in the rice fields of the Tagus estuary (Portugal)

    An estimate of the number of the birds that will be flying north to the Netherlands, as opposed to other countries. Limosa Black-tailed Godwits that pass through Iberia are on their way to a range of countries, stretching from the tiny population that breed in the UK, in the Ouse and Nene Washes, across to Germany in the east. This proportion was calculated by monitoring the movements of satellite-tagged individuals.

The results have just been published in a new paper, which also presents annual survival rates, obtained using colour-ring sightings. There is a full explanation of the methodology in the paper. You can also see maps from the satellite-tagging project on the King of the Meadows website.

postEstimating the size of the Dutch breeding population of Continental Black-tailed Godwits from 2007–2015 using resighting data from spring staging sites. Ardea 114: 213–225. doi:10.5253/arde.v104i3.a7

The authors are Rosemarie Kentie, Nathan R. Senner, Jos C.E.W. Hooijmeijer, Rocío Márquez-Ferrando, Jordi Figuerola, José A. Masero, Mo A. Verhoeven & Theunis Piersma.

Latest findings

Over the eight years of the survey work, the average decline in numbers of limosa Black-tailed Godwits has been 3.7% per year. Numbers appeared to go up between 2009 and 2011, when the calculated survival rate of young birds was high, but the magnitude of this perceived recovery may have been artificially elevated by an increase in the number of Icelandic birds. From WeBS counts in the United Kingdom, the number of islandica birds is continuing to rise.

Since 2011, the estimated annual decrease has been 6.3% per year. Such large declines can only occur if there is both low recruitment and reduced adult survival.

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Agricultural intensification has seriously affected Dutch Black-tailed Godwits

The estimated breeding population in the Netherlands in 2015 was 33,000 pairs, representing a drop of nearly 75% since 1967. However, the agricultural grasslands of the Netherlands are still the single most important stronghold for breeding limosa  Black-tailed Godwits using the East Atlantic flyway.

The authors finish with a sad conclusion. “Although enormous amounts of money and effort have been expended to conserve continental godwits, our findings make clear that these have been ineffective or insufficient.”

One wonders how much worse the situation would have been without Dutch and European support for Meadow Birds and the ‘King of the Meadows’ in particular?


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Estimating the size of the Dutch breeding population of Continental Black-tailed Godwits from 2007–2015 using resighting data from spring staging sites.  

The authors are Rosemarie Kentie, Nathan R. Senner, Jos C.E.W. Hooijmeijer, Rocío Márquez-Ferrando, Jordi Figuerola, José A. Masero, Mo A. Verhoeven & Theunis Piersma.


 GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

Wales: a special place for waders

From winter beaches to summer moorland and woodland, Wales provides essential habitats for waders. 

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There are thirty WaderTales blogs so far. Here’s a selection of ten that may well appeal to birdwatchers in Wales.

Winter beaches & estuaries

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Most Oystercatchers are being ringed with two letter engraved rings, along with two colour-rings: Photo Tómas Gunnarsson

Wales holds important populations of waders in the wintertime – everything from Bar-tailed Godwits from Siberia to Turnstones from Canada. Some of the Oystercatchers seen in sites such as the Burry Inlet or the Menai Strait are from Iceland, where they can be found alongside Redshanks and Golden Plover that have also arrived from the north. They emphasise the close links between Wales and Iceland when it come to birdlife.  Migratory decisions for Icelandic Oystercatchers explains how a new project is examining the costs and benefits of being a migrant. Welsh reports of Icelandic colour-ringed birds are helping to provide answers.

snipe-1Interestingly, while there are similar links between Ireland and Iceland, the migratory provenance of Welsh Snipe may be very different to that of Irish ones. A quarter of foreign-ringed Snipe reported in Ireland have been found to be wearing Icelandic rings but, so far, no Reykjavik-ringed Snipe have been spotted in Wales. Snipe & Jack Snipe in the UK and Ireland compares the migratory strategies of the two species and laments the decline of Common Snipe, as a breeding species.

Protecting key wintering sites is a high priority when it comes to wader conservation. A new BTO and WWT project aims to provide better information as to how species as diverse as Dunlin and Shelduck make use of the Severn Estuary. This is important work, with major relevance to discussions as to how power might be generated within the estuary. Tracking waders on the Severn urges birdwatchers to look for colour-marked birds. Initial results, shared at the recent International Wader Study Group conference, indicate that the home range of a Redshank is ten times as big as originally thought. It will be interesting to see what else this study reveals.

horse-and-flockHundreds of Welsh birdwatchers take part in the Wetland Bird Survey and the intensive work involved in periodic Low Tide Counts. These identify and monitor key sites and establish the most important feeding sites within estuaries. Whilst mud  and sand-flats are, of course, important to waders, so are roost sites. A place to roost discusses the importance of safe, high-tide roosts, especially in terms of energetics. I had not realised that it has been estimated that the cost of flying to and from roosts might account for up to 14% of a bird’s daily energy expenditure. That’s something to think about next time you see a dog chasing off a flock of roosting waders.

Passing through

whimbrel-mig-fig1There is exciting work going on in Wales to understand why so many Whimbrel spend time in the country in the spring. Whimbrels on the move summarises a recent paper about the movements of Icelandic, ringed Whimbrel. Since its publication, a new paper has shown that Whimbrel are able to fly between Iceland and west Africa in one jump but that they sometimes need to stop off on the way north. See Very rapid long-distance sea crossing by a migratory bird by José Alves and colleagues.

Breeding Waders

Wales provides homes to many breeding waders, from Ringed Plover on the coast, via Little Ringed Plover and Commons Sandpiper along rivers and into the moorland for Curlew and Dunlin, passing a forest with Woodcock en route. And that’s only giving a mention to half of the country’s breeding wader species.

CattleStarting on salt-marsh, Big-foot and the Redshank nest investigates appropriate cattle stocking levels for successful Redshank breeding. Although the work was undertaken in northwest England, there is no reason to believe that Welsh cattle area any less careful as to where they put their feet. There are several other blogs about Lapwings and Redshank on the WaderTales site.

We are all aware of the issues facing upland waders. The next blog was written to promote a survey in England, looking at the distribution of waders along the moorland/farmland interface, but the stories will have resonance with Welsh birdwatchers. All downhill for upland waders outlines changes to breeding numbers and distributions of waders breeding in England’s uplands.

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Curlews fly vast distances to spend the winter on the estuaries of Britain & Ireland (© Graham Catley)

Is the Curlew really near-threatened? considers the plight of breeding Curlew. It’s easy to understand why RSPB, BTO, GWCT and BirdWatch Ireland are focusing on this species How long will it be until breeding Curlew are lost from Wales, completely?

Predation is acknowledged as a major issue for Curlew but is this going to be a problem for Oystercatchers too? Oystercatchers: from shingle beach to roof-tops reveals a significant decline of the species in Scotland, mediated to some extent by range expansion in three dimensions. There’s a specific mention of the Burry Inlet control programme of the 1970s.

The strangest Welsh wader has to be the Woodcock – probing about in winter fields and nesting in forestry plantations. Conserving British-breeding Woodcock focuses on worrying results from the latest GWCT/BTO survey and work to reduce losses during the shooting season.

Further reading

Hopefully, this summary  gives a flavour of some of the issues being faced by Welsh waders and the research to which they are contributing. There are already 30 blogs in the WaderTales series, with one or two new blogs being produced each month. If you want to know how volcanoes affect breeding waders in Iceland, why Black-tailed Godwits wear colour-rings or if there are costs to carrying a geolocator have a look here.


GFA in IcelandGraham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.

Can habitat management rescue Lapwing populations?

Can a mosaic of habitats boost hatching success in grassland-breeding Lapwings?

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Lapwings are becoming more and more restricted in their distribution within the United Kingdom, with an increasing proportion dependent on a small number of lowland wet grassland sites, particularly nature reserves. Working in this habitat, a team from the RSPB and the University of East Anglia has been trying to work out if it is possible to substantially improve Lapwing productivity without using intensive, costly predator management, in the form of permanent electric fences.

Background

graphThe RSPB has been monitoring breeding waders on their Berney Marshes reserve in Norfolk for over 20 years. Even with fox control, a wader-friendly grazing regime and sensitive regulation of water levels, Lapwing nesting success on this site is still below 0.6-0.8 chicks per pairs in most years, which is the estimated range required for population stability (Macdonald & Bolton 2008a). Predation is the main issue that is still limiting productivity.

Previous work has shown that:

  • Providing areas of tall, dense grass (often along field verges) can encourage populations of small mammals, which are the main prey of most wader nest predators (Laidlaw et al 2012).
  • The lay-out of wet features can influence Lapwing nesting densities (Eglington et al 2008).
  • Nest survival is higher when Lapwing densities are higher (Macdonald & Bolton 2008b).

The team believe that these three factors – small mammal distribution, surface water and Lapwing nesting density – are very likely to influence the behaviour and distribution of red foxes, the key predator in this study area.

There is more background information in the WaderTales blog entitled A Helping Hand for Lapwings and in a perspectives article in Wader Study by Jen Smart.

ditchIn a recent RSPB/UEA project, Dr Becky Laidlaw has investigated these relationships further and has then used the trends that have been established to model different potential management scenarios. What could happen if nesting densities, wetness and the proximity of verges with small mammals could all be varied in the best ways possible? Is there a theoretical scenario in which productivity is high enough to fuel population growth?

The paper is published as: Scenarios of habitat management options to reduce predator impacts on nesting waders. Rebecca A. Laidlaw, Jennifer Smart, Mark A. Smart and Jennifer A. Gill 2016 Journal of Applied Ecology doi: 10.1111/1365-2664.12838

The right habitat mix?

Using relationships established from previous studies and collating seven years of information on over 1400 individual nesting attempts, Dr Becky Laidlaw and her colleagues from UEA and RSPB saw that, not only was nesting success being influenced by wetness and the proximity of tall grass, there were some subtleties relating to the way that habitats are distributed. Might it be possible to  redesign the site so as to create a patchwork that could achieve the required productivity levels? Becky had two variables to play with – verges and wet features.

Verges influence predation rates, with Lapwing nests further from tall vegetation areas having a higher likelihood of being predated. This makes sense if foxes are concentrating on catching small mammals in areas with high mammal densities, and are more likely to ignore eggs that are laid in short grass close to mammal-rich verges.

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There are plenty of wet features at Berney. The River Yare is in the foreground.

Water also influences wader nest predation rates. This is not surprising; if you are a fox, it is probably going to be harder to search for nests in a wet field with lots of pools and ditches than in a dry field. Interestingly, the study found that nests in the centre of dry fields were more at risk than those at the centre of wet fields. In a wet field, it’s riskier to nest along the edge, whilst in a dry field the risk increases the further the nest is from the edge.

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Part of a figure in Scenarios of habitat management options to reduce predator impacts, published in Journal of Applied Ecology by Laidlaw et al (Journal of Applied Ecology, 2016)

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The team want to see more Lapwing chicks. These are newly-hatched.

The study confirmed that isolated Lapwing nests are more at risk of predation, potentially because single pairs don’t benefit from the mobbing defensive behaviour provided by having plenty of nesting neighbours. They found a similar pattern with Redshank nest predation risk; these scarcer breeding waders appear to be protected by the presence of more Lapwing.

Scenario modelling

Becky then worked with Mark Smart, the RSPB manager with responsibility for Berney Marshes, to model some potential future management scenarios for the site. They worked out where it would be feasible to add or remove verges and increase or decrease surface wetness within fields. Becky then used existing relationships to predict what changes in nest predation rates might be expected. Were there management options that could significantly increase survival rates of nests?

ralphBecky compared the different modelled management scenarios with the long term average nest predation rate for the site. She found a significant (roughly 20%) reduction in nest predation could potentially be achieved with the addition of tall vegetation, but only for nests close to field edges in areas of high Lapwing nest density. Importantly, this sort of decrease in nest predation levels could potentially increase the number of chicks hatching by around 100 each year, but such management relies upon areas of sufficiently high Lapwing breeding density being available.

The influence of nesting density

The aim of this applied research was to find a way to manage breeding habitat for Lapwing that could be rolled out to areas of conservation-sensitive farming outside nature reserves. Given the subtleties of creating the right patchwork of wet features and long grass at Berney, it’s going to be tricky to get similar benefits on other sites. If habitat management alone is not enough, even when used alongside fox control, then what else can be done?

Becky has a possible answer. “The breeding density measure we are using is the number of active nests within 100 metres of a nest. It may therefore be important not only for nests to be clustered in fields with appropriate conditions, but also that they are at the same stage at the same time. Synchronous nesting is something that we think might be very important.”

fenceFrom data collected on RSPB reserves with and without electric fences (which exclude foxes), it is clear that fencing greatly increases the synchrony of nesting attempts (because most of the early nesting attempts are successful). Given that the density of active nests has a major effect on nest survival rates, increasing the number of nests active at the same time may well provide a greater level of protection, through the mobbing behaviour of Lapwing, and therefore lead to greater hatching success.

As part of a new piece of research (funded by NERC, a UK government research council), Becky and the UEA/RSPB team are going to test whether the provision of temporary electric fences for just the early part of the breeding season can provide sufficient protection to increase hatching success, as a consequence of nests being more synchronous. If early-reared chicks are more likely to fledge than late-reared chicks, there also may be additional knock-on benefits post-hatching and through to the recruitment stage.

Becky is hopeful. “We understand how wader predation rates are influenced by the proximity to verges, the accessibility issues caused by water and the mobbing, defensive behaviour of waders. We are now interested in determining the best way to use this information in management. With the new work with fences we’re going to be specifically exploring the importance of synchrony to both nest success and productivity”.

Scenarios of habitat management options to reduce predator impacts on nesting waders. Rebecca A. Laidlaw, Jennifer Smart, Mark A. Smart and Jennifer A. Gill 2016 Journal of Applied Ecology doi: 10.1111/1365-2664.12838

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GFA in IcelandGraham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.

 

WaderTales: a taste of Scotland

Here are four uniquely-Scottish WaderTales blogs to read:

scottish-wadertalesEstablishing breeding requirements of Whimbrel  focuses on the different habitat needs of adults and chicks in Shetland.

Oystercatchers: from shingle beach to roof-tops details significant declines in Scotland, at least partly explained by predation. An increasing number have now taken to nesting on roofs.

UK Dotterel numbers have fallen by 57% presents the results of an RSPB survey that was published in Bird Study.

Prickly problems for waders explains how SNH are trying to deal with introduced Hedgehogs in the Outer Hebrides, where they are a major problem for breeding waders.

And here are another six which may well appeal to Scottish birdwatchers:

  • NEWS and Oystercatchers focuses on the waders that  winter on coasts, instead of estuaries. It was written to promote the 205/16 coastal survey run by BTO.
  • A place to roost discusses the importance of safe, high-tide roosts, especially in terms of energetics. What are waders looking for?

There are 30 WaderTales blogs. The intention is to add one or two new blogs each month. You can sign up to receive an e-mail notification when a new one is published.


GFA in IcelandGraham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.

Black-tailed Godwits and Volcanic Eruptions

Around 360 earthquakes were detected in Iceland in the week beginning 4 December, which is pretty normal. Earthquakes can give hints about impending volcanic eruptions so they’re important to Icelanders –  and, by implication, to Icelandic waders too.

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In the long term, volcanic ash provides the nutrients that improve fertility, as you can read in How volcanic eruptions help waders, but short-term effects can be seriously negative. This was what Tómas Gunnarsson discovered when he went out to count godwit broods at what should have been the height of the 2011 breeding season. He found only two pairs that showed signs of having broods. Was the Grímsvötn eruption between 21 and 28 May to blame?

Assessing producivity

Iceland hosts internationally important breeding populations of several wader species, including almost the entire population of the islandica subspecies of Black-tailed Godwits. For several years, wader biologists in Iceland have been monitoring the breeding performance of Black-tailed Godwits in the Southern Lowlands, by counting pairs with broods along a 198 km transect. Their theory was that breeding performance would be better in warm years because of the advantages of early nesting in warm springs.

graphWith six years of data, a team drawn from the universities of Iceland, Aveiro (Portugal) and East Anglia (UK) have published a paper in the BOU Journal IBIS, which fouses upon the relationship between spring temperature and the number of Black-tailed Godwit broods. In the top graph, taken from the paper, it is clear that there is a lot of variation in productivity, with the lower graph showing a strong association between mean May temperatures and the number of Black-tailed Godwit pairs with chicks. What stands out is  the outlier for 2011 (open dot), which is excluded from the calculations that produce the regression line. For the five other years R² = 0.94, indicating a very close link between May temperature and productivity, as predicted. Using the mean temperature for May 2011, the number of pairs of godwits with chicks that might have been expected to have been seen in 2011 is about 25 – rather than just two.

The full methods can be viewed in this paper:

Effects of spring temperature and volcanic eruptions on wder productivity. Tómas Grétar Gunnarsson, Lilja Jóhannesdóttir, José A Alves, Böðvar Þórisson & Jennifer A Gill. IBIS (2017) DOI: 10.1111/ibi.12449

The ash effect

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Eyjafjallajokull in 2010

We all remember the eruption of Eyjafjallajökull in 2010. This produced copious amounts of ash, most of which was blown south to mainland Europe, disrupting air travel. Grimsvötn, which erupted in May 2011, was less famous but actually depositied a lot more ash in Iceland, especially in the Southern Lowlands.

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Ash  covered pools and clogged insect traps

On dry days, fieldworkers working in this study area used face masks to protect their respiration, as simply walking through vegetation disturbed large amounts of ash into the air. A layer of ash was frequently observed covering pools in wetlands and traps for invertebrate sampling were often clogged with ash. Short-term negative effects of volcanic dust on birds have been reported previously, probably acting through increased invertebrate mortality, and the low count of successful broods in the warm summer of 2011 seems to bear this out.

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An alarming parent godwit

By monitoring breeding Black-tailed Godwits in southern Iceland, the wader scientists have shown that volcanic activity can have a major impact  on bird productivity. Productivity was back to what appears to be normal (when corrected for mean temperature) by the next summer. The lack of recruitment in 2011 seems to have been reflected in a slight decrease in the counts of Black-tailed Godwits in the United Kingdom in the winter 2011/12 (as measured by WeBS counts), with a resumption in what is generally an upward population trend in 2012/13.

The rapid recovery of productivity in the year following the volcanic eruption (2012) indicates that the negative effects of the incident seem to be have been short in duration. Whimbrels in the same region were also affected by volcanic activity in the summer of the 2011 eruption (Katrínardóttir et al. 2015). In the long-term, the effects of volcanic activity on waders in Iceland are most likely to be positive, as volcanic dust recharges vegetated land with nutrients and buffers pH. Densities of waders across Iceland are generally higher where volcanic dust inputs are higher (Gunnarsson et al. 2015).

singleThis study shows how annual variation in productivity can vary greatly in response to rare and extreme events. As expected for a long-lived species, effects of a single year of very low productivity were short in duration and probably had a limited effect on the population growth rate. The pronounced effect that spring temperature has on annual variation in productivity is likely to be a more significant factor in the future population trajectory of waders, given the ongoing and rapid warming of Arctic and Sub-arctic regions.

Effects of spring temperature and volcanic eruptions on wder productivity. Tómas Grétar Gunnarsson, Lilja Jóhannesdóttir, José A Alves, Böðvar Þórisson & Jennifer A Gill. IBIS (2017) DOI: 10.1111/ibi.12449


GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

Overtaking on Migration

When two legs are better than one: the spring migration of Black-tailed Godwits.

headerThe winter range of Icelandic Black-tailed Godwits covers a relatively wide latitudinal spread, from southern Spain to Scotland.  Even though not at the extremes of this distribution, a flock of birds in Lisbon experiences very different mid-winter conditions to a flock of birds in Liverpool.  December days never get shorter than 9hr 27min in Lisbon, which is 2 hours more than in Liverpool, and the average maximum daytime temperature is 14⁰C, as opposed to 6⁰C.  On the negative side, it’s a lot further from Iceland to Portugal than it is to northern England.

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José Alves enjoying warm winter conditions in Portugal

In other studies (of Avocets and Cormorants, for instance) it has been shown that individual birds that winter close to their breeding areas are able to arrive back earlier in the spring than ones that winter further away.  This is not the case in Black-tailed Godwits and this paper, published in Oikos in 2012, explains why.

Overtaking on migration: does longer distance migration always incur a penalty? José A. Alves , Tómas G. Gunnarsson , Peter M. Potts , Guillaume Gélinaud , William J. Sutherland and Jennifer A. Gill

Background

A team from the universities of East Anglia (UK), Iceland and Aveiro (Portugal) has been monitoring the spring arrival dates of colour-ringed Icelandic Black-tailed Godwits since 2000. The most recent paper to use this data-set has shown that adult birds have remarkably fixed arrival times in Iceland (to within a few days), and that the advancing arrival of the godwit population has been driven by young birds travelling to Iceland for the first time (see wadertales.wordpress.com/2015/11/16/why-is-spring-migration-getting-earlier).  By tracking individual birds and the countries from which they travel, it is clear that the earliest arrivals are actually birds that winter in the southern part of the range – not the birds from northern and central parts of Great Britain, which have about 1500 km less far to travel.

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Black-tailed Godwits on the Tagus estuary (Lisbon)

For birds migrating south from arctic and subarctic breeding grounds, a trade-off might be expected between distance and conditions experienced during winter months. Birds travelling further south are likely to experience much more benign conditions, while those that undertake shorter flights expend less energy and may have the potential to return home earlier or to pick up clues as to the likely conditions they will face on breeding grounds in the early spring.

Work by Tómas Gunnarsson has shown links between arrival of Black-tailed Godwits in Iceland and subsequent breeding success. In areas where most territories are occupied early in the season, over half of pairs fledge youngsters whilst in areas where most territories are occupied later in the spring fewer than half of pairs are successful.  You can read more here.

The easy life in Portugal

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Portuguese rice fields provide alternative feeding opportunities for Black-tailed Godwits

José Alves studied Icelandic Black-tailed Godwits wintering in Portugal as part of his PhD at the University of East Anglia. One of the papers from this work, focusing on energetics and migration strategies, was published in Ecology in 2013:

Costs, benefits, and fitness consequences of different migratory strategies. José A. Alves , Tómas G. Gunnarsson , Daniel B. Hayhow, Graham F. Appleton, Peter M. Potts , Guillaume Gélinaud , William J. Sutherland and Jennifer A. Gill

energy-figThe paper shows that energetic conditions for wintering godwits are better in Portugal than further north in the winter range

  • Warmer air temperatures and considerably lower wind speeds mean that thermoregulatory costs, and hence energetic requirements, are lower for godwits wintering in west Portugal than in south Ireland or east England.
  • Black-tailed Godwits wintering in Portugal have access to larger numbers of bigger bivalves for the whole winter period. Birds wintering in eastern England or Ireland rarely find these big packages of protein.
  • On average, foraging for c.5 hours per day provides sufficient intake for a Portuguese-wintering Black-tailed Godwit.
  • In Ireland, the food supplies available on mudflats during the daylight hours of a tidal cycle are not sufficient, and godwits also forage on nearby grasslands.
  • In eastern England, rapid depletion of food supplies on estuaries means that resources become very limited in late winter, and are often not sufficient to meet the energy requirements of wintering godwits.

Clearly, Portugal is a great place to spend the winter. It’s just a long way from Iceland.

The Spring Overtake

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The direct route from Portugal to Iceland may be possible but most go via The Netherlands

Portuguese Black-tailed Godwits travel further to their winter site but they break their spring migration into two legs, with most birds moving to the Netherlands in February or March and others staging in France, Great Britain and Ireland. By using Colin Pennycuick’s model ‘Flight’ (Pennycuick, C. J. 2008. Modelling the flying bird. – Academic Press), José Alves and his colleagues investigated the range of spring migration strategies available to individuals, given their body masses. Of Portuguese-wintering Black-tailed Godwits, around 10% are predicted to be able to reach the breeding grounds in one flight. From sightings of colour-ringed birds, it is clear that the vast majority of Portuguese birds do not make direct flights. It is possible that some individuals fly straight to Iceland but no bird has yet been proven to take this option.

When a small number of Black-tailed Godwits were caught in Portugal, just prior to the normal departure time, the masses of individuals were remarkably good predictors of their subsequent movements.

  • The lightest male was predicted to be unable to reach even the first possible stop-over site, in France, and indeed this bird remained in Portugal throughout the breeding season.
  • Of two males with just sufficient mass to reach France, one did indeed get to France and the other remained in Portugal during that breeding season (but did migrate the following year).
  • The remaining seven males were predicted to be able to reach the major stop-over sites in the Netherlands or in east England (both of which are about 1750 km from west Portugal). Thanks to the wonderful network of observers, every one of these birds was spotted in these staging areas. These birds included RO-YGf (below)dutch-bird
  • The only two females caught were both later recorded in the Netherlands; the heavier one was seen shortly after ringing and the lighter one arrived later, possibly having spent time in France.

Black-tailed Godwits are well watched and often deliver day-by-day records. For this species, colour-rings are a cheap and simple technology with which to study migration. You can read more about the network of colour-ring readers in the WaderTales blog, Godwits & Godwiteers.

The Oikos paper goes on to discuss the strategies being employed by Black-tailed Godwits, relating these to the importance of getting to Iceland early. You can read more here:

Overtaking on migration: does longer distance migration always incur a penalty? José A. Alves , Tómas G. Gunnarsson , Peter M. Potts , Guillaume Gélinaud , William J. Sutherland and Jennifer A. Gill

In Conclusion

Portuguese Black-tailed Godwits make full advantage of benign winter conditions in Portugal and then fly north very early in spring. By moving to the Netherlands (or Britain & Ireland) they are taking up pole position for the race to Iceland.


GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

A place to roost

Safe roost sites are important for waders such as Black-tailed Godwits

top-picIt has been said that Black-tailed Godwits are the laziest birds in the world, usually in a frustrated tone while waiting for a marked bird to wake up and reveal the rest of its colour rings. Roosting is not laziness, however; it’s an important resource conservation strategy in the daily balance of energy inputs and outputs.

When Black-tailed Godwits are feeding in tidal systems they have a limited amount of time each day to access the shellfish and worms that make up their diet. These foods are unavailable over the high-tide period, and sometimes in the lull between the ebb and flood, so birds conserve energy by gathering together at roosts. They seek out sites which are safe and sheltered and go to sleep – often for several hours if undisturbed. Theunis Piersma and colleagues have shown that sleep is the most energy efficient form of activity for shorebirds.

In two interesting papers, focusing on Red Knot and Great Knot in Roebuck Bay, North-Western Australia, Danny Rogers and colleagues showed that choice of roost sites seems to involve several criteria:

  • Birds try to find a roost as close as possible to feeding sites, probably to reduce travel costs between feeding areas and high-tide roosts.
  • In particular, birds appear to turn down feeding opportunities that take them further from preferred roost sites.
  • Open roosting sites that provide clear views of any approaching predators seem to be preferred
  • Availability of safe night-time roosts seems to be more restricted, with birds flying further to find a suitable site to wait out the high tide period.
  • The estimated ‘commuting costs’ associated with flying to and from these roosts accounted for between 2% and 8% of daily energy expenditure.
  • Flocks of Knot that were disturbed at roosts and forced to fly around for thirty minutes had an estimated increase in their daily energy expenditure of c 13%.
  • roosting-curlew

    These Curlew, roosting on the shores of the Humber, are minimising energy expenditure in very cold conditions

    Temperatures in Roebuck Bay can frequently exceed 38⁰C, and the waders chose wet sites in which they could keep their feet and legs cool. That’s not a problem for waders wintering in the UK.

The details can be found here:

What does this mean for Black-tailed Godwit in UK conditions?

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Waders often roost in mixed flocks. These birds are resting on an Icelandic beach after crossing the Atlantic

Although the facts, figures and conclusions listed above relate to Red Knot and Great Knot, the authors point out that they gather in mixed roosts with other species to which similar decision-making might apply. The Australian studies took place in very hot conditions but many of the factors influencing roosting site choice are likely to also apply to our cold and wind-swept estuaries in NW Europe. For instance, a study of Knot on the Dee Estuary by Mitchell et al in England estimated that costs of commuting to roosts could account for 14% of daily energy expenditure.

energy-figEnergetic constraints are likely to present different issues for arctic waders that spend the non-breeding season in the northern hemisphere than for ones that choose to cross the equator, and experience warmer conditions and heat stress. Even within Europe, the energetic balances that waders can experience on different estuaries can vary widely. In their 2013 Ecology paper on Black-tailed Godwit energetics, Costs, benefits, and fitness consequences of different migratory strategies  José Alves and colleagues showed that mild weather and abundant food supplies result in a positive energy balance for godwits wintering on the Tagus estuary in Portugal and, to a lesser extent, the estuaries of south Ireland. In east England estuaries, however, the costs of keeping warm can sometimes exceed the energy available from the food supplies (see figure). In such circumstances, an undisturbed roost, located as close as possible to feeding areas may well be especially important.

Consequences of roost loss

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Colour-marked Redshank demonstrated the individual consequences of habitat loss

Although it is very hard to demonstrate population-level consequences of removing roosting sites, we have some clues about the how birds respond to removal of roosts and foraging sites from impact assessment work carried out by the BTO on Redshank in the Cardiff Bay area. When this bay was closed and flooded for commercial development, Redshanks lost both feeding areas and traditional roosting sites. Tracking of colour-ringed Redshanks showed that displaced birds moved to new feeding areas and roost sites up to 19 km away, but mostly stayed close-by on the mudflats of the River Rhymney. Cannon-net catches of these flocks provided measurements of bird mass before and after the closure of the Bay, which revealed that adult Redshank from the Bay had difficulty in maintaining body condition in the first winter following closure and that their survival rates in subsequent winters remained lower than birds that had previously been settled in the Rhymney area. Three papers are essential reading for anyone interested in the consequences of displacements caused by development projects.

ynrx-for-blogA key point of both the Knot work in Australia and the Redshank impact assessment study in Wales is the energetic costs to individuals that can result from the disruption caused by the loss of roosting or foraging sites. Indeed, individual waders may even have favoured locations within roosts that they consistently use. For example, at Gilroy Nature Park, a shallow pool where up to 3500 of the Black-tailed Godwits that feed on the Dee estuary in NW England regularly gather to roost, observers of colour-ringed birds have noticed that marked individual godwits (eg YN-RX pictured here) are often seen in exactly the same place within the pool and flock.  Losing a roosting site of which individuals have such detailed knowledge, and forcing flocks of birds to find alternative roosting locations, may therefore have bigger consequences than just the kilometres covered.

Importance of individual sites

mapThe total number of Icelandic Black-tailed godwits was estimated to be 47,000 in 2004, a figure that is likely to be closer to 60,000 now as the population has continued to grow. This means that a flock of 3,000 birds represents about 5% of the total of the entire breeding population. There is a small number of sites across the United Kingdom that hold these sorts of numbers at different stages of the year. According to the latest figures from the Wetland Bird Survey, numbers on the Wash and Humber estuaries in east England peak at averages of 8198 and 3413 in September, there are 4339 Black-tailed Godwits on the Welsh side of the Dee estuary in October and 5909 on the English side in November. The mean count on the Thames also peaks in November (5883). As the winter progresses, numbers on the nearby Ribble estuary rise to a mean of 4234 in January, there is a mean maximum of 3236 on the Washes in February and 3191 on the Blackwater in March. Although all of these sites are important to Icelandic Black-tailed Godwits throughout the non-breeding period, the different timing of peak counts illustrates the reliance of Icelandic birds on a network of sites. To get a feel for the range of strategies used by individual birds, see Godwits and Godwiteers.

Conservation

horse-and-flock

Roosting Black-tailed  Godwits at Gilroy Nature Reserve share their pool with a horse and Canada Geese

While estuarine feeding areas across Europe are well safeguarded, through the network of Special Protection Areas, roost sites are not always as well served, especially if birds spend the high tide period on sites outside the SPA boundary of their foraging areas, such as the freshwater pool at Gilroy Nature Reserve, inland of the Dee Estuary. Some roost sites such as North Killingholme Haven Pits on the Humber have been included within a designated SPA formed by the adjacent mudflats but others, such as Gilroy, are discrete sites outside the SPA. Maintaining the wader populations that forage on our estuarine mudflats may depend upon our capacity to protect their safe roosting sites, even if they are not currently designated.


GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

Establishing breeding requirements of Whimbrel

Breeding Whimbrel may be associated with wet heaths but chicks need small pools and ditches too

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One of the advantages for waders (shorebirds) is that parents can lead their chicks to suitable feeding areas almost as soon as they are hatched. This means that the habitat in which parents choose to secrete their nests can be very different to the habitat in which their youngsters will later forage.

ad-for-blogAs part of a study into the potential impacts of a large wind farm proposal on Shetland, a team from Alba Ecology Ltd and Natural Research Projects Ltd collected data on the habitat associations of wader species, particularly Whimbrel, on Mainland Shetland. A new paper, in the BTO journal Bird Study shows that habitats used by Whimbrel chicks for feeding are significantly different to those used by adults for feeding and nesting.

Habitat characteristics of breeding Eurasian Whimbrel Numenius phaeopus on Mainland Shetland, Scotland, UK by Kate Massey, Peter Cosgrove, Fergus Massey, Digger Jackson & Mark Chapman

Fourteen sites across Mainland Shetland were studied, in order to identify the three main requirements of Whimbrel – adult territorial and foraging habitats, nest site habitats and chick feeding habitats. The sites were spread across central and west Mainland Shetland, focusing on areas regularly used by breeding Whimbrel. Between them, these held between 90 and 100 pairs, out of a local total of 150 local pairs.

chick-for-blogWhilst adult Whimbrels used blanket bog, dominated by ling heather, cottongrass and other species associated with wet heath, when both nesting and feeding, the structure of habitats used by chicks was very different. These were characterized by small, wet and often linear features, with plenty of mosses and plants such as purple moor-grass and bulbous rush. The presence of these flashes, ditches and former peat-cuttings may be crucial to the successful breeding of Whimbrels.

Sad times for the Curlew family

curlew IUCN

Based on IUCN BirdLife assessments

As outlined in the blog Is the Curlew really near-threatened? we have probably already lost 2 out of 8 of the members of the curlew family – definitely Eskimo Curlew and possibly Slender-billed Curlew. Although Whimbrels are not currently causing official concern, there is certainly a need to be watchful. This paper is therefore an important addition to the written information about the habitat requirements of the species. The conclusions reached by the authors may well be of interest to scientists tackling tricky issues relating to the conservation of European Curlew. Across Wales and Ireland, breeding populations have been decimated (literally).

 Providing the right habitat for Shetland’s Whimbrel

 For Shetland’s Whimbrel, the habitat differences between adult feeding/nesting locations and chick foraging locations were very striking and suggest that the presence of both types of habitat may be of importance. Chicks move out of the heavily grazed open heather areas, in which nests are often made, and into wetter and taller, mixed, and structurally-diverse vegetation, where it is easier to hide from predators such as gulls, corvids and skuas, and to find food. If suitable habitat for Whimbrel chick foraging is limited, then chick growth and survival may be compromised. This paper suggests that management aimed at benefiting breeding Whimbrel needs to address the habitat needs of chicks, in terms of wet features, as well as the habitat needs of adults for foraging and nesting. You can read more in the paper.

habitat-for-blog

Grazed heather areas (left) are favoured by feeding and nesting adults, while chicks prefer wet flashes (right). Photos: Peter Cosgrove

 Work on other upland wader species has shown that food availability, vegetation structure and cover from predators may at least partly explain habitat preferences of chicks. When tracking Golden Plover families in northern England, Mark Whittingham and colleagues found that chicks selected the edges of marshy habitats. They recommended that drainage ditches should be blocked, in order to provide more suitable feeding habitat. An added benefit of this sort of measure is that more water is held on moorland, which helps to reduce flooding downstream.

Lowland wet grasslands in Broads

Shallow ditches increase Lapwing productivity: Mike Page/RSPB

As Peter Cosgrove, one of the authors of the new paper has commented, “The more I read and discover about wader chicks, the more I see the importance of small, wet flushes with cover – maybe this is a general feature of many species?” As you can read in A helping hand for Lapwings, the provision of wet features, particularly foot-drains, is crucial to the successful fledging of species in a more open landscape.

A matter of scale?

Creating the right habitat mosaic for adults and chicks will depend upon the scale of the movements of family parties of the wader species that is causing conservation concerns. Tómas Gunnarsson reports that family groups of Icelandic Black-tailed Godwits can cover large distances. One brood of small chicks (less than five days old) was found a week later 3 km away. Whimbrels may be able to select areas with suitable nesting and nearby chick-rearing potential or perhaps they can also move their chicks longer distances, if necessary? Research into the movements of family parties might tell us whether moving chicks for a kilometre or more could have adverse consequences, in terms of growth or survival. Presumably, adults would prefer to find the right mix of habitats within relatively close proximity, which suggests that managing grazed heath to provide a suitable mosaic of cover for nests, areas of short vegetation and wet features may be a sensible conservation prescription for Whimbrel.

Habitat characteristics of breeding Eurasian Whimbrel Numenius phaeopus on Mainland Shetland, Scotland, UK by Kate Massey, Peter Cosgrove, Fergus Massey, Digger Jackson & Mark Chapman


GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

 

 

 

Snipe & Jack Snipe in the UK and Ireland

This blog first appeared as an article in Shooting Times and Country magazine. It has been amended to provide more web links.

snipe-header

A wisp of Common Snipe

There’s a big difference between the number of Common Snipe and Jack Snipe we see in the United Kingdom each winter, with an estimated 1,100,000 of the former and 110,000 of the latter, according to the authors of Population Estimates of Bird in Great Britain and the United Kingdom. They remind us that Jack Snipe are hard to find and identify and warn that the total of 110,000 is a contender for ‘least reliable’ of the hundreds that have been compiled for this mammoth stock-take.

size-table

Comparative measurements (summarised from work by Guy-Noel Olivier)

In theory, therefore, for every ten Common Snipe we see we ought to see one Jack Snipe. Telling them apart is mostly a matter of size (see table) and there’s a useful identification video that has been produced by the British Trust for Ornithology. Both species make good use of their striped, cryptic plumage to avoid detection but Jack Snipe take the art to the next level, hiding against or under a tussock until the last possible moment and then exploding from beneath a person’s feet. Given the closeness of approach, perhaps Jack Snipes might be more obvious and their numbers exaggerated?

jack-puddle

Jack Snipe probing in mud

In the winter months, Jack Snipe are not as closely associated with wetlands as are Common Snipe, preferring longer vegetation, such as that to be found in muddy, cow-poached rough grazing marsh, to the open edges of larger bodies of water. For the tiny Jack Snipe, a cow’s hoof-print forms an ideal pool in which to probe. One of the areas that birdwatchers go to see Jack Snipe is Glasgow. Strange though it may seem, several of the wetland areas within the city limits hold small numbers of birds, especially in autumn, when migrating Jack Snipe pass through Britain, on their way from Scandinavia to wintering areas in south-west Europe. Members of the local ringing group have focused a lot of effort on this species, catching individuals by dragging a mist-net through the rough, wet, reedy grassland and ringing birds that have jumped from the ground as the net passed over them. See blog by Gillian Dinsmore.

jack-flight

Jack Snipe are relatively long-winged

Jack Snipe are well designed for migration, with much bigger wings for the size of the body than the Snipe. Unlike Common Snipe, many of which migrate in flocks, or wisps, Jack Snipe are thought to travel mostly alone and at night. They cover long distances, with some birds from Russia crossing the Sahara and those from eastern areas of Siberia travelling to eastern Africa, India and southern coastal countries of mainland Asia. The birds that winter in the British Isles have much less far to travel than the majority of the population, therefore.

Common Snipe, which are much bigger and more common than Jack Snipe, start to appear in their wintering areas as early as August. The pioneering birds are juveniles; most adults moulting at least some of their flight feathers before flying south and west in September and October. We know this because many French hunters have provided wings to scientists studying the age and sex structure of the population in that country. Moulting is an energetically expensive part of any bird’s life, so autumn feeding conditions are presumably generally good enough for moult to have been at least started, if not finished, before birds leave the breeding areas. Not every bird manages to fit in a full moult before it’s time to move south, however, with one in six adults shot in France found to be in suspended moult, having shed and moulted some primary feathers before migration, with a view to completion in the wintering grounds. A slightly smaller number have a mixed age of secondary flight feathers and about a quarter delay completion of covert moult.

snipe-1

Common Snipe

Although most of the Common Snipe we see in Britain in the wintertime have come from Scandinavia and mainland Europe, Ireland has a strong additional connection to Iceland. A quarter of foreign-ringed Common Snipe discovered in Ireland or Northern Ireland have been found to be wearing Icelandic rings, compared to 1 out of 255 in England, none in Wales and just 10% in Scotland. This and lots of other fascinating facts about migration come to light because hunters kindly send information about ringed birds to The British Trust for Ornithology, which is ‘mission control’ for ringing in both the UK and Ireland. This information is available on-line via the BTO website.

Across Europe, although there is almost certainly a decline in the number of Common Snipe, probably linked to man’s incessant drive to drain wetlands, there is no suggestion as yet that Common Snipe should be added to the list of species of conservation concern. For British and Irish breeding birds the situation is very different, however. By the time of the first national bird surveys, some 50 years ago, we had been turning wetlands into farmland for as much as 2000 years and, since then, numbers of Common Snipe may well have fallen by a further 90% in the areas in which they are still breeding. There has been a major shrinkage of the species’ range since 1968-72. Losses are shown as downward triangles in the map from the latest Bird Atlas, published by the British Trust for Ornithology. The rate of decline across England, Wales, southern Scotland and much of Ireland in the shorter period since 1988-91 emphasises just how quickly the species is being lost. It can only be a matter of time until Common Snipe is added to the red list of species of conservation concern in the UK, in order to highlight the perilous plight of our breeding population.

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drumming-snipe

Displaying Common Snipe

A displaying Common Snipe is a magical thing – flying around with real purpose, climbing into the sky and vibrating its tail feathers in a stooping descent. Our grandparents could have heard them drumming on grazing marshes anywhere in the country and just imagine what the fens of eastern England must have been like 500 years ago. These days, most people in southern Britain will have to visit a nature reserve even to have a chance to share that same magic. I am lucky enough to go to Iceland every summer, where I can still easily see a dozen Common Snipe displaying at the same time above areas of wet grassland.  If you want anything like the same sort of experience in the UK, you’ll probably need to travel to the Outer Hebrides.


GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

 

Bar-tailed Godwits: migration & survival

Putting the flags out –  to learn more about one of the most amazing species of migrating wader.

Ruth banner

When we caught 505 Bar-tailed Godwits on the Wash, on the east coast of England, on 29 August 1976 we thought that we would add hugely to our knowledge of the species’ migration but we were disappointed. In the last six years, by adding leg-flags to just 248 birds, the Wash Wader Ringing Group has learnt a lot more.

Forty years ago

On 29 August 1976, in the days of stubble-burning, we had covered four cannon nets with fine, black burnt chaff to hide them almost completely. We knew that the big tide would push birds off the saltings and over the sea wall, there were decoys to pull the birds into the right 1% of a vast, flat field and the weather was good. Everything was ready. I was in a one-man, cabbage-crate hide, in line with my set of two nets. I remember seeing one Redshank look at the decoys and descend, pulling down a vast cloud of over 2000 Bar-tailed Godwits. There were some concerns about birds being too close to one of the nets on my line so we fired three nets, catching 505 bar-tailed godwits and 44 other waders.

Cathy ad and juv

Juvenile with moulting adult

A catch of 505 Bar-tailed Godwits seemed like a game-changer, including 22 that were already wearing rings. 483 new birds were bound to make a huge difference to our understanding of the species’ migration patterns and survival probabilities … surely? Up until that day, the Wash Wader Ringing Group (WWRG) had ringed a total of 1136 Bar-tailed Godwits so we were adding over 40% to the total, using harder rings with a much longer life-expectancy than those added as early as 1959.

This was a moulting flock; an autumn drop in numbers and a previous recovery of a bird in Spain suggested that many birds would spend the winter elsewhere but where? As luck would have it, only one of the birds from August 1976 has ever been found abroad – a bird shot in France in February 1985. The only British recoveries have been a bird found dead in Yorkshire in November 1976 and seven birds found around the Wash between 1979 and 1999. As to subsequent recaptures, 38 birds have been caught again by the WWRG, five of which were retrapped for a third time. With all the best models in the world, these figures are not enough to give a reasonable estimate of survival and there is no way that a change in survival rate could be picked up.

It’s pleasing to report that one bird was still alive on 21 February 2003 – over 28 years after ringing – but even this is not the longevity record for a BTO Bar-tailed Godwit. That’s held by another WWRG bird that was ringed on 22 August 1974 and last recaptured on 4 August 2008 – nearly 34 years later. Perhaps one of the 1976 birds is still alive and waiting to be caught again?

Bar-tailed Godwit migration

Since the 1976 catch, WWRG has been a bit more fortunate in its foreign recoveries of metal-ringed Bar-tailed Godwit, with 2 recoveries in Mauritania, one in Guinea Bissau and another on a ship off Guinea, out of a total of 12 BTO-ringed birds found in Africa. A bird caught in Teesmouth on 13 October 1982 was in Western Sahara five days later, which may give an indication of the timing of post-moult movement. The map alongside shows the full set of BTO recoveries (purple) and foreign-ringed birds found in Britain & Ireland (orange). The dots show the westward post-breeding movement from Russia to the Atlantic coast of Europe and the onward migration of thousands of birds to Africa.

One of the fascinating things about migration is the way that different populations of the same species have developed radically different migration patterns since the last Ice Age, the global maximum extent of which was reached only 20,000 years ago. At the same time that the Bar-tailed Godwits we see in Western Europe are making relatively modest journeys west and south in late summer, some of those of the baueri subspecies are undertaking nine-day, non-stop flights from Alaska to New Zealand. The physiological processes and navigational techniques that birds on the Pacific flyway have mastered would amaze their European cousins. To read more about flyway evolution for Arctic waders, and Knot on particular, see a Review by Theunis Piersema (Journal of Ornithology, 2011).

Conservation Status

Bar-tailed Godwits are classified as near-threatened by BirdLife International and the IUCN. There are four recognised subspecies facing various threats, as shown in the species fact-sheet here. 

Sam winter gloves

Bar-tailed Godwits wintering on the Wash are of the lapponica subspecies

Two subspecies visit the Wash Special Protection Area (SPA); lapponica from Norway through to western Siberia and taymyrensis from central Siberia. Two subspecies, menzbieri and baueri, use the East Asian-Australasian Flyway and are both undergoing extremely rapid declines, in large part due to severe habitat loss in the Yellow Sea. As a result of severe problems for waders using this flyway, the species has been uplisted to Near Threatened (BIrdLife International).

Satellite-tagging has revealed the impressive trans-oceanic migration routes of individuals between Alaska and New Zealand and shown the importance of the Yellow Sea for birds as they return north in the spring. Colour-rings and flags have shown that there has been a sudden drop in survival rates for Bar-tailed Godwits and other species using sites in China and other rapidly developing countries of South-East Asia, leading to urgent calls for conservation initiatives at an international scale. You can read more about this emerging story in these three papers.

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Learn more about the amazing migration of Bar-tailed Godwits on the New Zealand Science Learning Hub

Contrasting extreme long-distance migration patterns in bar-tailed godwit Limosa lapponica. Phil Battley et al. Journal of Avian Biology. 10.1111/j.1600-048X.2011.05473.x 

Simultaneous declines in summer survival of three shorebird species signals a flyway at risk. Theunis Piersma at al. Journal of Animal Ecology. 10.1111/1365-2664.12582

Declining adult survival of New Zealand Bar-tailed Godwits during 2005–2012 despite apparent population stability. Jesse Conklin et al. Emu. http://dx.doi.org/10.1071/MU15058

For Bar-tailed Godwits wintering in western Europe there is currently less immediate conservation concern, although there are warming conditions in their breeding grounds and over-fishing and emerging diseases of shellfish are known to be affecting estuaries on both sides of the North Sea. Things are more worrying in West Africa, where numbers have declined from 746,000 to 498,000 over a period of 30 years, according to a report by van Roomen et al. Some of these birds spend time in the Wash in the autumn on their way south.

Status of coastal waterbird populations in the East Atlantic Flyway. With special attention to flyway populations making use of the Wadden Sea. van Roomen et al.

Flying the flag

Cathy gluing

Each bird wears a two-letter flag and a white colour-ring (shown here)

Given the worsening conservation status of Bar-tailed Godwits and the gaps in our understanding of what is happening to birds that visit the Wash SPA, the WWRG decided that it would help if birds could be monitored through colour-ringing. That way, the movement and survival of individuals can be monitored using a telescope instead of relying on recapture.

The flagging of Bar-tailed Godwits on the Wash has dramatically increased the number of records of birds subsequent to ringing but the scheme is still in its early days. Flagging started in August 2010 but the first significant catch did not take place until 11 February 2012, when 56 birds was flagged. According to Phil Atkinson, who runs the WWRG database for the species, one third of the birds from this catch have been resighted alive in the four years since that catch (compared to 1% recapture rate for metal-ringed birds in the four years after the 1976 catch).

Cathy KAMost resightings have been on the Wash and those from elsewhere have tended to confirm what was known from metal ringing. A moulting bird on the Wash was seen on the Wirral (northwest England) in the same autumn, showing that birds moulting on the Wash can move elsewhere in Northwest Europe to winter. A non-moulting bird, caught at Terrington on 30 September 2011, was resighted at Ebel Khaznaya, Mauritania 50 days later. These two resightings confirmed that the Wash is an important site not only for the wintering Fenno-Scandinavian and western Siberian lapponica breeding populations but also central Siberian taymyrensis birds, that pass through in autumn to wintering areas in West Africa. The majority of overseas records have come from the Wadden Sea in spring and autumn, when birds have been on return passage to the breeding areas. There’s a 1996 summary of migratory movements of metal-ringed WWRG birds here:

The origins, moult, movements and changes in numbers of Bar-tailed Godwits Limosa lapponica on the Wash, England, Bird Study.  http://dx.doi.org/10.1080/00063659609460996 

Aivar Estonia

UV was spotted in Estonia in August 2012

By the end of 2015, 248 Bar-tailed Godwits had been colour-ringed and 92 of them seen again, many locally on the Wash. These high resighting rates are a consequence of focused searches by WWRG members and reports from birdwatchers submitting their records to sightings@wwrg.org.uk. Over the next few years it will be possible to estimate annual survival probabilities and to monitor how these change in the medium to long term. As was shown in the Yellow Sea, spotting a dramatic drop in colour-ring return rates provides evidence that development pressures are having an impact upon migratory species. Worsening conditions in the breeding grounds or wintering areas could well be detected through a more gradual but no less serious reduction in survival rates.


GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton